Approximately one-third of the drugs in the United States Pharmacopoeia are water-insoluble or poorly water-soluble. Many currently available injectable formulations of such drugs carry important adverse warnings on their labels that originate from detergents and other agents used for their solubilization. Oral formulations of water-insoluble drugs or compounds with biological uses frequently show poor and erratic bioavailability. In addition, water-solubility problems delay or completely block the development of many new drugs and other biologically useful compounds.
Two alternative approaches for insoluble drug delivery are microparticles which involves forming a phospholipid stabilized aqueous suspension of submicron sized particles of the drug (see U.S. Pat. Nos. 5,091,187; 5,091,188 and 5,246,707) and microdroplets which involves forming a phospholipid stabilized oil in water emulsion by dissolving the drug in a suitable bio-compatible hydrophobic carrier (see U.S. Pat. Nos. 4,622,219 and 4,725,442).
The pharmacokinetic properties of both oral and injectable microparticle formulations are dependent on both the particle size and phospholid surface modifier. However, with certain water insoluble compounds the current employed methods of particle size reduction are problematic. Thus, the overall objective of this invention is to develop a novel process based on the use of compressed fluids, including supercritical fluid technology, that yields surface modifier stabilized suspensions of water insoluble drugs with an average particle size of 100 nm to about 300 nm and a narrow size distribution. The inventive process is robust, scalable and applicable to a wide range of water-insoluble compounds with biological uses.